The objective of the Core unit is to provide continued high quality analytical support for the metabolic studies in the PERC. This aim can be achieved efficiently and in a cost-effective way, by having a centralized Core facility utilized by a number of investigators. This is particularly necessary for stable isotope and mass spectrometry, because of the complicated nature of methods and the high cost of purchasing and maintaining the necessary equipment. Over the past several years, all of these objectives have been successfully achieved. The Core Metabolism Laboratories have had a major impact on the productivity and the quality of research of various investigators in the PERC. The GC-MS Laboratory has developed new innovative stable isotope methods for the study of metabolism in the pregnant subject and the newborn infants. Analytical techniques for the following stable isotope labelled substrates are established in our laboratories: glucose, urea, alanine, leucine, lysine, serine and glycine, lactate, palmitic acid, glycerol, and ketones. All of the methods are now routine analysis. In addition, the analytical technique for the measurement of 13C enrichment of blood bicarbonate has been refined. A more recent addition has been the quantitative analysis of a-keto acids of branched-chain amino acids on GC-MS & HPLC. These techniques were important in order to measure the precursor pool enrichment for quantifying protein synthesis. Services provided will include sample analysis, help in interpretation, supervision and consultation. The Core is also responsible for the maintenance and adequate functioning of the sophisticated analytical instruments. All of the metabolism protocols utilizing stable isotope tracers will use the Core Laboratory.